1. Field The present invention relates to the sterilization of dental handpieces and particularly to sterilization apparatus that provides for the sterilization of both the inside and outside surfaces of dental handpieces.
2. State of the Art
The need to sterilize dental equipment, particularly dental handpieces, between uses has long been recognized. An urgency to provide more effective sterilization procedures has developed with the increasing awareness of the communicable disease hazards confronting dentists and their patients. These hazards include hepatitis, which is extremely difficult to treat, and AIDS, for which there is presently no effective cure. The AIDS epidemic has made dentists very aware that they, and their patients, may be exposed to the HIV virus through contact with blood and other body fluids.
One of the shortcomings of sterilization processes and apparatus conventionally used in the dental field is that the sterilant often fails to penetrate into the openings and passageways of dental handpieces. Dental handpieces may have a single internal passage or they may have a plurality of such passages. They are generally constructed to receive plug-in utility lines. These lines are coupled to the passages during use of a handpiece, and decoupled from the lines and the handpiece following use. When a handpiece is turned off, a slight vacuum is characteristically created at its tip. This suction tends to pull contaminant fluids, such as saliva and/or blood, into the internal passages of the handpiece. The separated handpiece is then subjected to a sterilization procedure, usually in a hermetically sealed chamber.
Chemical vapors are presently the sterilants of choice, because they provide a less corrosive environment than steam, but these vapors cannot effect adequate sterilization unless brought into intimate contact with the contaminating organisms under attack. Penetration is essential to achieve this contact, but no suitable system for providing such contact of chemical vapors to the internal surfaces of dental handpieces has been available.
U.S. Pat. No. 4,752,444 discloses a method for sterilizing a dental handpiece. According to that patent, a pneumatic pump is used to force a liquid sterilant through the interior of the handpiece. Next, a supply of water is pumped through the handpiece to flush away any sterilant residue. Then a supply of oil is passed through the handpiece to lubricate its mechanical components, suck as a turbine assembly or bearings. At the same time the liquid sterilant is passed through the dental handpiece, the exterior of the handpiece is soaked in a bath of sterilant.
U.S. Pat. No. 4,410,492, discloses a method which comprises the circulation of a sterilant gas through a contaminated medical device to sterilize exposed surfaces. The sterilant gas remains within the lumen of the device for an effective period of time, and thereafter is removed by purging with sterile air or other inert gas. The apparatus disclosed includes a chamber having an access door through which materials to be sterilized are introduced and removed, a pump, and control valves. In practicing the methods, a contaminated object, such as an endoscope, is placed in the chamber and is coupled to a discharge outlet. A pump is connected to the discharge outlet, outside the chamber. The chamber is sealed. Atmosphere is pumped from the chamber. The chamber is heated. A sterilant gas (ethylene oxide vapor) is circulated and recirculated, using the pump and valves, through and around the object for a time sufficient to effect sterilization. The sterilant is pulled through an opening at one end of the object, through the object and out an opening in an end of the object at the coupling to the chamber. The sterilant gas is removed, and sterile air or other gas is admitted, circulated around and through the object and out of the chamber through the pump and control valves.
U.S. Pat. No. 4,810,469 discloses a method for sterilizing an artificial organ with high pressure steam in an autoclave. Sterilized high pressure liquid, maintained at a temperature sufficient for sterilization, is passed through the artificial organ to raise its inner temperature to approximately a sterilization temperature. The organ is simultaneously heated externally to a sterilizing temperature, and is maintained at that temperature for the time required to sterilize the organ. A low temperature sterilant is then passed through and around the organ to cool it.
None of the sterilization systems currently available fill the need for apparatus that can be conveniently used in a dental office to sterilize equipment that is needed on a repeat basis throughout a working day. Particularly, there remains a need for a system that can quickly, easily and effectively sterilize the dental handpieces used by dentists with successive patients. Ideally, such a system should be suitable for the delivery of chemical vapor sterilant.